Haskell:如何使用attoparsec从ByteString中读取嵌套列表

Question

我有一个带有嵌套列表的文本文件(~300 MB大),类似于这个:

[[4, 9, 11, 28, 30, 45, 55, 58, 61, 62, 63, 69, 74, 76, 77, 82, 87, 92, 93, 94, 95], [4, 9, 11, 28, 30, 45, 55, 58, 61, 62, 63, 69, 74, 76, 77, 82, 87, 92, 93, 94],[4, 9, 11, 28, 30, 45, 55, 58, 61, 62, 63, 69, 74, 76, 77, 82, 85, 87, 92, 93, 94, 95]]

这是我的程序将文件读​​入haskell Integer列表:

import qualified Data.ByteString as ByteStr

main :: IO ()

-- HOW to do the same thing but using ByteStr.readFile for file access?
main = do fContents <- readFile filePath 
          let numList = readNums fContents
          putStrLn (show nums)

这适用于小文本文件,但我想用来ByteString快速读取文件.我发现readByteString 没有函数,你应该在attoparsec中编写自己的解析器,因为它支持解析ByteStrings.

我如何使用attoparsec解析嵌套列表？

Answer 1

数据似乎是JSON格式,因此您可以使用可以使用的Data.Aeson decode函数ByteString

import qualified Data.ByteString.Lazy as BL
import Data.Aeson
import Data.Maybe

main = do fContents <- BL.readFile filePath 
          let numList = decode fContents :: Maybe [[Int]]
          putStrLn (show $ fromJust numList)